Shingles vaccine most promising common drug to potentially prevent Alzheimer’s -research

A new study has identified three existing medications that could be repurposed to treat or prevent Alzheimer’s disease.

The research funded by Alzheimer’s Society and led by the University of Exeter, is published today in Alzheimer’s Research and Therapy. It found that a shingles vaccine (Zostavax), is the most promising existing medicine that could be repurposed to treat or prevent Alzheimer’s disease. Viagra (sildenafil) and a drug used to treat motor neurone disease (riluzole) also showed strong promise.

Dementia is the UK’s biggest killer, with around one million people in the UK living with the condition. One in three people born today will develop dementia in their lifetime – but there is currently no cure. 

Developing entirely new drugs from scratch can take 10 to 15 years and can cost billions of pounds – with no guarantee they will work. Repurposing medicines already approved for other conditions offers a quicker, safer and cost-effective route to potential new treatments for dementia.  

The research is part funded by the National Institute for Health and Care Research (NIHR), Exeter Biomedical Research Centre and NIHR HealthTech Research Centre in Brain Health. 

In this study, an international panel of 21 dementia experts from universities, hospitals and the pharmaceutical industry, as well as people affected by dementia, carried out a review of 80 existing drugs to identify which might have the greatest potential to treat or prevent Alzheimer’s, responsible for more than half of all the diagnosed cases of dementia.  

After several rounds of careful review, the panel reached a consensus on the three ‘priority candidates’ for further investigation. These drugs were selected as they all targeted relevant mechanisms involved in Alzheimer’s disease, showed promise in cell and animal studies of Alzheimer’s and are known to be safe to use by older people 

• Shingles vaccine (Zostavax)– research suggests a link between the shingles virus and dementia. Changes to the immune system are known to play a role in Alzheimer’s and the vaccine interacts with the immune system in way that could help to protect against some of these changes.1 

• Sildenafil (Viagra) –  shown to help protect nerve cells and reduce build up of the protein tau in the brain. In tests involving mice, it also improved cognition, thought to be due to increasing blood flow to the brain.  

• Riluzole – currently used to treat motor neurone disease. In animal studies riluzole has shown promising results in improving cognition and reducing levels of tau.  

The experts recommended that these drugs now be tested in clinical trials to understand their benefit for people with or at risk of Alzheimer’s disease. 

Of these three treatments, the shingles vaccine was found to be the most promising, particularly as it requires a maximum of two doses and has a strong safety record. Previous studies show people who had the jab could be 16% less likely to develop dementia. 

The lead researchers now hope to carry out a large clinical trial of this shingles vaccine in the UK, using the to monitor participants involved. PROTECT is an online registry where once a year, participants are asked to answer  questionnaires about themselves, their lifestyle and health, and can take part in brain health research. 

Five other drugs were shortlisted but did not meet the criteria for the ‘priority candidates’ list. These included fingolimod (used in MS), vortioxetine (used to treat major depressive disorder), microlithium (used to treat depression), dasitinib (used for leukaemia) and cytisine (used in anaesthetics). 

Dr Anne Corbett, Professor of Dementia Research at the University of Exeter, said: “Beating dementia will take every avenue of research – from using what we already know, to discovering new drugs to treat and prevent the condition. 

“Drug repurposing is a vital part of that mix, helping us turn today’s medicine for one condition, into tomorrow’s treatment for another. 

“It’s important to stress that these drugs need further investigation before we will know whether they can be used to treat or prevent Alzheimer’s. We now need to see robust clinical trials to understand their true value and know for certain if they are effective to treat or prevent Alzheimer’s.” 

Prof Fiona Carragher, Chief Policy and Research Officer at Alzheimer’s Society, said: “Dementia devastates lives, but we believe research will beat it. 

“Years ago, we saw aspirin being repurposed from being a painkiller to helping people reduce their risk of heart attack or stroke. This is what we want to see in the field of dementia, and why we believe drug repurposing is one of the most exciting frontiers in dementia research.” 

Reference:

Corbett, A., Sultana, J., Stych, K. et al. Drug repurposing for Alzheimer’s disease: a Delphi consensus and stakeholder consultation. Alz Res Therapy 17, 237 (2025). https://doi.org/10.1186/s13195-025-01895-4